Field of the Invention
The invention relates to the joystick pilot valve equipped with the structure for preventing oil leakage, and more specifically, to the joystick pilot valve equipped with the structure for preventing oil leakage comprising the boot which may keep the alien material from penetrate in the inner portion and may keep the operation oil from leaking to the outer portion and one or more of the drain holes which may make the oil leaked from the spool called the main part flow into the inner portion of the joystick.
Moreover, the invention relates to the joystick pilot valve wherein the check valve for making the leaked oil flow into the joystick valve is set up in the drain hole and wherein the operation oil (hydraulic fluid) collected in the operation oil chamber of the valve body may not be again leaked to the outer portion of the valve body.
Description of the Related Art
Generally, the pilot valve manipulated by the joystick is widely used in the construction heavy equipment such as the excavator and load, and the actuator may be operated for driving the working machine like the boom or the bucket in response to the pilot signal pressure generated when the spool is operated by the manipulation of the driver.
As described in FIGS. 1 and 2, in case of the joystick pilot valve of the prior art, the joystick lever 1 manually operated by the worker (or the driver) is connected to the valve body 3 by the joint 2 and a plurality of push rods 5 are protruded from the upper side of the valve body 3. Accordingly, if the joystick lever 1 is manipulated, the pushing cam 10 selectively presses the push rods 5 and the spool 8 connected to the lower part of the push rod 5 may move up and down from the respective spool hole 9.
The hydraulic fluid chamber 6 is formed in the valve body 3 and the hydraulic oil is fed back to tank through the return port formed on the central part of the valve body 3. And the hydraulic oil (hydraulic fluid) supplied to the hydraulic fluid chamber 6 from the external hydraulic pump and the actuator is ejected to the respective supply port 7 of the valve body and the hydraulic oil acts as the actuator signal pressure of the working machine. In other words, a plurality of the supply ports 7 (ordinarily, 4) may be formed at the valve body 3, the supply port 7 connected with the external hydraulic pump and the actuator may be formed at the inner portion of the valve body 3, the hydraulic fluid chamber 6 connected with the external operation oil tank is equipped in the upper side of the supply port 7, and he hydraulic fluid chamber 6 may be connected with the supply port 7 or may be blocked from the supply port 7 according to the operation of the spool 8 equipped in the respective supply port 7. While the pushing cam 10 seesaws with the mechanical operation means in which the operator operates the joystick lever 1, the spool 8 may be pressed down, and when the spool 8 is pressed down, the hydraulic fluid chamber 6 may be connected with the supply port 7 in which the pressed spool 8 is installed, the hydraulic oil in the hydraulic fluid chamber 6 is supplied to the supply port 7 in which the pressed spool 8 is installed so that the supplied hydraulic oil may be acted as the actuator signal pressure of the working machine like the excavator. Therefore, the bucket of the excavator is operated, and the spool 8 is returned upward by the spring 14. That is, according to said joystick pilot valve, because the respective spools 8 block the flow passage between the respective supply ports 7 and The hydraulic fluid chamber 6, the working machine (such as bucket of the excavator and so on) is maintained at the state of stop. If, at the state of stop of the working machine, the flow passage is opened by the spool 8 which is operated by the operation of the joystick lever 1 of the driver (or the worker), the signal pressure (the hydraulic fluid pressure) through the supply port 7 connected to the hydraulic fluid chamber 6 may be supplied to the actuator, and for example, the boom of the load may be lengthened or be shortened, or the bucket of the excavator may be operated. Meanwhile, while the spool 8 returns to the original state by the force of spring 14, the hydraulic fluid returns to the hydraulic fluid chamber 6 through the return port formed in the central part of the valve body 3.
By the way, in case of the joystick pilot valve of the prior art, there is a problem that while the spool 8 linearly moves up and down by the push rod 5, the leakage of the hydraulic oil may be caused, and the foreign substance (dust etc.) introduced into boot (the boot covering the connection part of the joystick lever 1 and the valve body 3) may be mixed with the leaked hydraulic oil (hydraulic fluid) so that contamination may be caused. The leakage of the hydraulic oil is caused at the position between the guide hole 4 of the valve body in which the push rod 5 is ascended and descended and the outer periphery of the push rod 5, in other words, the position shown as LP in FIG. 1.
Moreover, as time goes by, the joystick lever 1 is unable to stand in the place but inclines due to oil leak, while the joystick lever 1 inclines, the spool 8 pressed down with the push rod 5 descends and the hydraulic fluid is supplied to the joystick valve. Therefore, there is a problem that malfunction of the valve may be caused.